#include <bits/stdc++.h>

using namespace std;
int n;
int lst, num, ans;

int ask(int x) {
    int a;
    cout << "+ " << x << endl;
    cin >> a;
    return a;
}

bool check(int x) {
    int diff = n - x + lst;
    if (diff >= n) {
        diff -= n;
        num--;
    }
    ans += diff;
    lst = x;

    return ask(diff) > num;
}

void answer(int x) {
    cout << "! " << x << endl;
}

int main() {
// #ifdef LOCAL
//     freopen("in.txt", "r", stdin);
//     freopen("out.txt", "w", stdout);
// #endif
    cin >> n;
    int l = 1, r = n - 1;
    while (l < r) {
        int mid = (l + r + 1) >> 1;
        if (check(mid)) {
            l = mid;
        }
        else {
            r = mid - 1;
        }
        num++;
    }
    answer(l + ans);
    return 0;
}